Electric double layer capacitor

ABSTRACT

An electric double layer capacitor having an electrode rolled body contained in an outer packaging can. The electrode rolled body includes a positive electrode plate having a positive electrode foil, on both sides of which an active substance is applied, a negative electrode plate having a negative electrode foil, on both sides of which the active substance is applied, and a separator interposed between these electrode plates, and is obtained by winding the above parts. The negative electrode foil is electrically connected directly to a bottom of the outer packaging can so that heat generated in an interior of the electric double layer capacitor is efficiently transferred to the outer packaging can from the negative electode foil. The negative electrode foil has a greater thickness than that of the positive electrode foil, which is not electrically connected to the outer packaging can, so that heat quantity transferred is made large.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric double layer capacitor inwhich electric double layers are formed at Interfaces between electrodesand an electrolyte and electricity is stored in the electric doublelayers.

2. Description of the Related Art

An electric double layer capacitor is an electricity charging anddischarging element. An example of such an electric double layercapacitor is disclosed in, for example, Japanese Patent Laid-OpenPublication No. HEI-10-294102 entitled “Electricity Storing Element”.

The disclosed electric double layer capacitor comprises an electroderolled body formed by overlapping a positive electrode plate, a negativeelectrode plate and a separator interposed therebetween to wind the samein a rolled manner. A lower end of the negative electrode plate isconnected electrically to a negative collecting plate, which serves as anegative electrode terminal. An upper end of the positive electrodeplate is connected electrically to a positive collecting plate, whichserves as a positive electrode terminal. After the electrode rolled bodyin such a state is contained in a bottomed, cylindrical-shaped outerpackaging can and an electrolyte is poured into the outer packaging can,the outer packaging can is closed by a cover. The positive collectingplate is electrically connected to the cover. The negative collectingplate is electrically connected to the outer packaging can.

With the above-mentioned electric double layer capacitor, heat generateddue to electric resistance generated from the electrode rolled body andthe like at the time of, for example, charging heats the electrolyte.Accordingly, to maintain the service life of an electric double layercapacitor over a long term, it is necessary to discharge the generatedheat to the atmosphere. FIG. 15 hereof shows a schematic constitution,in which heat of the above-mentioned electric double layer capacitor isdischarged.

In FIG. 15, an electric double layer capacitor 500 is constructed suchthat a negative collecting plate 505 is interposed between a negativeelectrode plate 502 of an electrode rolled body 501 and a bottom 504 ofan outer packaging can 503 to electrically connect the negativeelectrode plate 502 and the negative collecting plate 505 to each otherto connect the negative collecting plate 505 electrically to the bottom504 of the outer packaging can 503.

The electric double layer capacitor 500 comprises a first connection506, which electrically connects the negative electrode plate 502 andthe negative collecting plate 505 to each other, and a second connection507, which electrically connects the negative collecting plate 505 andthe bottom 504 of the outer packaging can 503 to each other. Therefore,heat generated in the electric double layer capacitor 500 is dischargedto the atmosphere from the outer packaging can through the firstconnection 506 and the second connection 507.

However, because the first connection 506 and the second connection 507are small in area, heat quantity transferred through the firstconnection 506 and the second connection 507 becomes small. Therefore,heat transfer quantity generated in the electric double layer capacitor500 is held down by the first connection 506 and the second connection507, which is responsible for temperature rise in the electric doublelayer capacitor 500 to affect the service life thereof.

Further, with the electric double layer capacitor disclosed in JapanesePatent Laid-Open Publication No. HE-10-294102, the positive collectingplate covers an upper end of the positive electrode plate, and so itacts as an obstacle when an electrolyte is filled into the electroderolled body. Therefore, it takes time to fill the electrolyte into theelectrode rolled body.

Japanese Patent Laid-Open Publication No. HEI-10-294102 furtherdiscloses a positive collecting plate having slits formed on both sidesof radially extending convex ridges. Such a positive collecting platewill be described with reference to FIG. 16 hereof.

FIG. 16 shows, in an enlarged scale, a part of the positive collectingplate having the slits formed on both sides of the convex ridges. Theconvex ridges 601 of the positive collecting plate 600 are used to bendan upper end 604 of a positive electrode plate 603 in an electroderolled body 602, and the convex ridges 601 are welded to bent portions605 of the upper end 604.

Because the positive collecting plate 600 has slits 606, 606 on bothsides of the convex ridges 601, it is possible to fill an electrolyteinto the electrode rolled body 602 through the slits 606, 606.

Since both ends 605 a of the bent portions 605 of the positive electrodeplate 603 extend to the slits 606, 606, however, a part of the slits606, 606 is closed by the both ends 605 a of the bent portions 605.Therefore, when an electrolyte is filled into the electrode rolled body602 from the slits 606, 606, the both ends 605 a of the bent portions605 act as an obstacle, and so it is difficult to efficiently fill theelectrolyte from the slits 606, 606.

Further, with the electric double layer capacitor disclosed in theabove-mentioned Japanese Patent Laid-Open Publication No. HEI-10-294102,a leaf-spring shaped pressing member is mounted on a side of the coverin order to electrically connect the cover to the positive collectingplate, and the pressing member is brought into electrical contact with acentral projection of the positive collecting plate. However, thepressing member contacts locally with the projection, and so the contactarea therebetween is small. Therefore, electric current flowing in localcontact portions between the pressing member and the projection isrestricted.

To flow large electric current at contact portions is important inimproving the performance of an electric double layer capacitor.

Hereupon, FIG. 17 shows a conventional electric double layer capacitorcapable of flowing a relatively large electric current.

Referring to FIG. 17, an electric double layer capacitor 700 isconstructed such that an outer packaging can 707 contains therein anelectrode rolled body 701 in a state, in which a negative collectingplate 704 is electrically connected to a lower end of a negativeelectrode plate 702 of the electrode rolled body 701 and a positivecollecting plate 705 is electrically connected to an upper end of apositive electrode plate 703. The negative collecting plate 704 isconnected electrically to a bottom 708 of an outer packaging can 707.The positive collecting plate 705 is electrically connected to a cover709. The outer packaging can 707 is filled with an electrolyte.

The positive collecting plate 705 is formed centrally with an upwardlyextending projection 706. The projection 706 is inserted into a hole 709a formed in the cover 709. The projection 706 is welded to the cover709. The projection 706 is formed to have a relatively large diameter tobe large in cross sectional area. Therefore, a relatively large electriccurrent can be made to flow to the projection 706 to improve theperformance of the electric double layer capacitor 700.

It is necessary to reduce the electrode rolled body 701 in manufacturingerror because it is required that a reference dimension Hi from thebottom 708 of the outer packaging can 707. which serves as a negativeelectrode, to a tip end 706 a of the projection 706, which serves as apositive electrode, to be uniform. Therefore, a height hi of theelectrode rolled body must be kept uniform by decreasing the electroderolled body 701 in manufacturing error.

However, the electrode rolled body 701 shown in FIG. 17 is constructedby overlapping and winding the positive electrode plate, negativeelectrode plate and a separator in a rolled manner, and so displacementupon winding to generate manufacturing error is liable to occur.Therefore, to reduce the electrode rolled body 701 in manufacturingerror to keep the height h1 of the electrode rolled body 701 uniform, aninstallation of high accuracy is necessary and it is difficult to holddown cost of an electric double layer capacitor due to the increasedinstallation cost.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide an electricdouble layer capacitor capable of efficiently discharging heat generatedin an interior thereof.

It is a second object of the invention to provide an electric doublelayer capacitor enabling efficiently filling an electrolyte into aninterior of an electrode rolled body of the electric double layercapacitor.

It is a third object of the Invention to hold down cost of an electricdouble layer capacitor.

In a first aspect of the present invention, there is provided anelectric double layer capacitor having an outer packaging can containingtherein an electrode rolled body obtained by Interposing a separatorbetween a pair of a positive electrode plate having a positive electrodefoil, on both sides of which an active substance is applied, and anegative electrode plate having a negative electrode foil, on both sidesof which the active substance is applied, and winding them,characterized in that the negative electrode foil is electricallyconnected directly to a bottom of the outer packaging can, and thenegative electrode foil has a greater thickness than that of thepositive electrode foil, which is not electrically connected to theouter packaging can.

In this manner, in the first aspect of the invention, the negativeelectrode foil is electrically connected directly to the bottom of theouter packaging can, so that locations of electric connection in a heatconductive path can be reduced to thereby provide an increase in heattransfer quantity. Accordingly, heat generated in the electric doublelayer capacitor can be efficiently transferred to the bottom of theouter packaging can from the negative electrode foil, and so heatgenerated in the electric double layer capacitor is efficientlydischarged to the atmosphere. And the electric double layer capacitor Isextended in service life.

Further, in the invention, the negative electrode foil connected to thebottom of the outer packaging can has a greater thickness than that ofthe positive electrode foil. Therefore, the negative electrode foil canbe increased in cross sectional area to increase heat transfer quantity,so that heat in the electric double layer capacitor can be efficientlytransferred to the bottom of the outer packaging can. Besides, thenegative electrode foil is increased in thickness to be enhanced inrigidity, so that the electric double layer capacitor is improved invibration-proof quality. Further, only the negative electrode foil ismade thick and the positive electrode foil is made thin, whereby theelectrode rolled body is not made large, and so the electric doublelayer capacitor does not become large sized.

In a second aspect of the present invention, there is provided anelectric double layer capacitor having an electrode rolled body obtainedby overlapping and winding a pair of electrode plates, which serve aspositive and negative electrodes, and positive and negative collectingplates, which are mounted to edges of the electrode rolled body andthrough which charging is effected on the electrode plates anddischarging is effected from the electrode plates, characterized in thatat least the positive collecting plate of the collecting plates includesa plurality of convex ridges extending radially from central portionsthereof and projecting toward the electrode rolled body, and openings ornotches formed to be positioned between adjacent convex ridges, and thatthe convex ridges are pressed against the electrode rolled body to formbent portions on upper and lower ends of the electrode plates, and theconvex ridges are joined to the bent portions by welding to permit anelectrolyte to be filled into the electrode rolled body through theopenings or notches.

In this manner, in the second aspect of the invention, a plurality ofthe convex ridges are formed on the collecting plates, and the openingsor notches are formed to be positioned between adjacent convex ridges.Accordingly. the convex ridges are pressed to form the bent portions onthe upper and lower ends of the electrode plates. and the convex ridgesare joined to the bent portions by welding to thereby enablingseparating the openings or notches from the bent portions. Therefore,when an electrolyte is filled into the electrode rolled body from theopenings or notches, the bent portions do not interfere with filling ofthe electrolyte and the electrolyte is rapidly filled.

In a third aspect of the present invention, there is provided anelectric double layer capacitor comprising: an electrode rolled bodyformed by overlapping one of electrode plates on the other of electrodeplates and winding the same in a rolled manner; a bottomed,cylindrical-shaped outer packaging can containing therein the electroderolled body and connected electrically to one end of the one ofelectrode plates; a collecting plate connected electrically to the otherof electrode plates of the electrode rolled body contained in the outerpackaging can; and a cover covering the outer packaging can; and whereinthe cover is formed centrally thereof with a hole, from which acylindrical portion is extended outside, and a projection formedcentrally of the collecting plate is inserted into the cylindricalportion to an extent not to project from the cylindrical portion, andwherein the cylindrical portion and the projection are welded and sealedat a weld on an inner peripheral surface of the cylindrical portion.

In this manner, in the third aspect of the invention, the cylindricalportion is mounted to the cover, and the projection is formed on thecollecting plate to be capable of being inserted into the cylindricalportion. Therefore, even when a relatively large manufacturing error isproduced on the electrode rolled body, the manufacturing error of theelectrode rolled body can be accommodated by moving the projection inthat range, in which the projection will not project from thecylindrical portion, so that it is possible with a simple constitutionto keep a reference dimension of the electric double layer capacitoruniform. Accordingly, when the electrode rolled body is wound,manufacturing error is allowable to some extent, and so it is possibleto hold down cost of an electric double layer capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain preferred embodiments of the present invention will be describedin details hereinbelow, by way of example only, with reference to theaccompanying drawings, in which

FIG. 1 is a cross sectional view showing an electric double layercapacitor according to a first embodiment of the invention;

FIG. 2 is a view illustrating an action of the electric double layercapacitor shown in FIG. 1;

FIG. 3 is a cross sectional view showing an electric double layercapacitor according to a second embodiment of the invention;

FIG. 4 is a perspective view showing the relationship between anelectrode rolled body and a positive collecting plate shown in FIG. 3;

FIG. 5 is a perspective view showing a part of the electrode rolled bodyshown in FIG. 3;

FIG. 6 is an enlarged cross sectional view showing a part shown in FIG.4;

FIGS. 7A to 7F are views illustrating the order of mounting of theelectrode rolled body and the positive collecting plate in the secondembodiment;

FIGS. 8A and 8B are views illustrating a state of welding when radial,convex ridges are positionally deviated from set movements of anelectron beam welding apparatus;

FIGS. 9A and 9B are views illustrating actions of another embodiment anda comparative example when an electrolyte is filled into an interior ofthe electrode rolled body of the electric double layer capacitor;

FIG. 10 is a plan view showing a first modification of the positivecollecting plate in the electric double layer capacitor according to theembodiment of FIGS. 9A and 9B of the invention;

FIG. 11 is a plan view showing a second modification of the positivecollecting plate in the electric double layer capacitor according to theembodiment of FIGS. 9A and 9B of the invention;

FIGS. 12A and 12B are views illustrating an action when the electroderolled body is loaded in an outer packaging can;

FIG. 13 is a view the relationship between a cylindrical-shaped portionand projections of Me positive collecting plate;

FIG. 14 is a schematic view showing an electric double layer capacitorin a state, in which welding is carried out at predetermined locationsand sealing is effected after the electrode rolled body is loaded in theouter packaging can;

FIG. 15 is a cross sectional view showing part of a known electricdouble layer capacitor;

FIG. 16 is an enlarged, perspective view showing part of a positivecollecting plate in the known double layer capacitor; and

FIG. 17 is a cross sectional view showing the known double layercapacitor

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is merely exemplary in nature and is in no wayintended to limit the invention, its application or uses.

In FIG. 1, an electric double layer capacitor 10 comprises an electroderolled body 12 for storing electricity, a collecting plate 20 connectedelectrically to a positive electrode plate 13 of an electrode rolledbody 12, a bottomed, cylindrical-shaped outer packaging can 30, whichcontains the electrode rolled body 12 thus connected and is connectedelectrically to a negative electrode plate 16, an electrolyte 37 filledin the outer packaging can 30, and a cover 40 closing the outerpackaging can 30.

The electrode rolled body 12 is constructed such that the positiveelectrode plate 13 and the negative electrode plate 16 overlap oneanother with a separator 18 interposed therebetween and are rolled rounda roll core 19 in a rolled fashion.

The positive electrode plate 13 comprises a belt-shaped positiveelectrode foil 14, and an active substance 15, 15 applied to both sidesof the positive electrode foil 14 except a positive electrode foil upperend 14 a of the positive electrode foil 14. The positive electrode foilupper end 14 a projects above the electrode rolled body 12. The positiveelectrode foil upper end 14 a is bent inward to be connectedelectrically to the collecting plate 20. The positive electrode foil 14is, for example, an aluminum foil or stainless steel foil, and theactive substance 15 is, for example, activated carbon.

The negative electrode plate 16 comprises a belt-shaped negativeelectrode foil 17, and an activated carbon 15, 15 applied to both sidesof the negative electrode foil 17 except a negative electrode foil lowerend 17 a of the negative electrode foil 17. The negative electrode foillower end 17 a projects below the electrode rolled body 12. The negativeelectrode foil lower end 17 a is bent inward to be connectedelectrically to a bottom 31 of the outer packaging can 30.

The negative electrode foil 17 is of an aluminum foil or stainless steelfoil having a greater thickness than that of the positive electrode foil14. The negative electrode foil 17 is set to have a thickness thatpermits heat generated in the electric double layer capacitor 10 to beefficiently discharged to the atmosphere and can endure when theelectric double layer capacitor 10 oscillates and that makes theelectrode rolled body 12 compact.

The separator 18 is an insulating paper that is interposed between thepositive electrode plate 13 and the negative electrode plate 16 toprovide insulation between the positive electrode plate 13 and thenegative electrode plate 16 and is formed with small holes so as not tointerfere with flow of ions.

The collecting plate 20 is constructed such that an upwardly extendingprojection 22 is formed centrally of a disk 21 and a plurality of convexridges 25 extend radially toward an outer periphery of the disk 21 fromthe projection 22. The projection 22 has an opening 22 a. The opening 22a mounts thereon a safety valve 27.

The convex ridges 25 are tapered such that they increase in heighttoward the outer periphery of the disk 21 from a center thereof.Therefore,pressing the collecting plate 20 against the positiveelectrode foil upper end 14 a of the positive electrode plate 13 cancause the convex ridges 25 to bend the positive electrode foil upper end14 a of the positive electrode plate 13 inward. Accordingly, a bentportion 14 b of the positive electrode foil upper end 14 a thus bentinward is connected electrically to the convex ridges 25 of thecollecting plate 20.

The outer packaging can 30 is formed of an electrically conductivematerial to be in the form of a bottomed cylinder. The bottom 31 of theouter packaging can 30 is provided centrally thereof with a projection32. A plurality of convex ridges 35 extend radially toward an outerperiphery of the bottom 31 from the projection 32.

The convex ridges 35 are tapered such that they increase in heighttoward the outer periphery of the bottom 31 from the projection 32formed on the bottom 31. Therefore, pressing the bottom 31 of the outerpackaging can 30 against the negative electrode foil lower end 17 a ofthe negative electrode plate 16 can cause the convex ridges 35 to bendthe negative electrode foil lower end 17 a inward. A bent portion 17 bof the negative electrode foil lower end 17 a thus bent inward isconnected electrically to the convex ridges 35 of the bottom 31.

The cover 40 comprises an outer ring 41 and a central cylindricalportion 42, each of which is formed of an electrically conductivematerial and both of which are joined by an insulating ring 44. The ring41 is welded to an opening 36 of the outer packaging can 30 to close theouter packaging can 30. In this manner, the cover 40 is more rigidlymounted to the outer packaging can 30 by welding the ring 41 to theopening 36 of the outer packaging can 30 than by mounting with caulking.

The projection 22 of the collecting plate 20 is inserted into an opening43 of the cylindrical portion 42. The projection 22 and an innerperipheral surface of the cylindrical portion 42 is joined by welding.

As shown in FIG. 2, the negative electrode foil lower end 17 a of thenegative electrode foil 17 is connected directly to the bottom 31 of theouter packaging can 30. Therefore, locations of connection in a heatconductive path comprise only a connection s48 between the negativeelectrode foil s17 and the bottom 31 of the outer packaging can 30. Thatis, because the negative electrode foil is not connected to the outerpackaging can through any negative collecting plate as in the prior art,locations of connection can be less than in the prior art.

Generally, connections are small in area and so small in heat transferquantity. Therefore, locations of connection in a heat conductive pathare reduced to thereby provide an increase in heat transfer quantity, sothat heat generated in the electric double layer capacitor 10 can beefficiently transferred to the bottom 31 of the outer packaging can 30from the negative electrode foil lower end 17 a of the negativeelectrode foil 17. Accordingly, heat generated in the electric doublelayer capacitor 10 is efficiently discharged to the atmosphere asindicated by arrows.

Further, the negative electrode foil 17 connected to the bottom 31 ofthe outer packaging can 30 is made thicker than the positive electrodefoil 14 not electrically connected to the outer packaging can 30. Sinceheat transfer quantity is in proportion to cross sectional area, heattransfer quantity can be increased by an amount the negative electrodefoil 17 is increased in cross sectional area. Accordingly. heatgenerated in the electric double layer capacitor 10 is efficientlytransferred to the bottom 31 of the outer packaging can 30 by thenegative electrode foil 17 to be discharged to the atmosphere.

In this manner, reduction in locations of connection in a heatconductive path and thickening of the negative electrode foil 17 make itpossible to prevent heat from accumulating in an interior of theelectric double layer capacitor 10 to extend the service life of theelectric double layer capacitor 10.

In the case where the electric double layer capacitor 10 is loaded on avehicle, vibrations of the vehicle are transmitted to the electricdouble layer capacitor 10, and so a vibration-proof quality is requiredof the electric double layer capacitor to enable the same to adequatelyendure vibrations of the vehicle. Hereupon, the electric double layercapacitor 10 according to this embodiment is designed to have thickenedthe negative electrode foil 17 connected to the bottom 31 of the outerpackaging can 30. Therefore, the negative electrode foil 17 can beincreased in rigidity, so that it becomes possible to improve thevibration-proof quality of the electric double layer capacitor 10.

In the case where the electric double layer capacitor 10 is loaded on avehicle, it is necessary to arrange the electric double layer capacitor10 in a limited space. Therefore, the electric double layer capacitor 10is required to be small in size. Hereupon, only the negative electrodefoil 17 connected to the bottom 31 of the outer packaging can 30 isthickened and the positive electrode foil 14 is made thin. Therefore,large sizing of the electrode rolled body 12 is suppressed as much aspossible.

Further, while an explanation has been given to an example, in which thenegative electrode foil lower end 17 a of the negative electrode foil 17is bent Inward to be connected directly to the bottom 31 of the outerpackaging can 30, the negative electrode foil lower end 17 a of thenegative electrode foil 17 may be connected electrically to the bottom31 of the outer packaging can 30 without being bent.

FIG. 3 is a cross sectional view showing an electric double layercapacitor according to a second embodiment of the invention.

In FIG. 3, an electric double layer capacitor 100 comprises n electroderolled body 112 for storing electricity, a collecting late (positivecollecting plate) 120 connected electrically to one of electrode plates(positive electrode plates) 113 of an electrode rolled body 112, acollecting plate (negative collecting plate) 150 connected electricallyto the other of the electrode plates (negative electrode plate) 116 ofan electrode rolled body 112, a bottomed, cylindrical-shaped outerpackaging can 130, which contains the electrode rolled body 112, anelectrolyte 37 filled in the outer packaging can 130, and a cover 140closing the outer packaging can 130.

The electrode rolled body 112 is constructed such that the positiveelectrode plate 113 and the negative electrode plate 116 overlap oneanother with a separator 118 interposed therebetween and are rolledround a roll core 119 in a rolled fashion.

The positive electrode plate 113 comprises a belt-shaped positiveelectrode foil 114, and an activated carbon 115, 115 applied to bothsides of the positive electrode foil 114 except a positive electrodefoil upper end 114 a of the positive electrode foil 114. The positiveelectrode foil upper end 114 a of the positive electrode foil 114projects above the electrode rolled body 112. The positive electrodefoil upper end 114 a is bent inward to be connected electrically to thepositive collecting plate 120. The positive electrode foil 114 is, forexample, an aluminum foil or stainless steel foil.

The negative electrode plate 116 comprises a belt-shaped negativeelectrode foil 117, and an activated carbon 115, 115 applied to bothsides of the negative electrode foil 117 except a negative electrodefoil lower end 117 a of the negative electrode foil 117. The negativeelectrode foil lower end 117 a of the negative electrode foil 117projects below the electrode rolled body 112. The negative electrodefoil lower end 117 a is bent inward to be connected electrically to thenegative collecting plate 150. The negative electrode foil 117 is, forexample, an aluminum foil or stainless steel foil.

The separator 118 is an insulating paper that is interposed between thepositive electrode plate 113 and the negative electrode plate 116 toprovide insulation between the positive electrode plate 113 and thenegative electrode plate 116.

The negative collecting plate 150 is constructed such that an downwardlyextending projection 152 is formed centrally of a disk 151 and aplurality of convex ridges 155 extend radially toward an outer peripheryof the disk 151 from the projection 152.

The projection 152 is constructed such that a large diameter portion 152a is formed centrally of the disk 151 to extend downward and a smalldiameter portion 152b is formed to extend further downward from thelarge diameter portion 152 a to form a step 153.

The convex ridges 155 are tapered such that they increase in heighttoward the outer periphery of the disk 151 from a center thereof.Therefore, pressing the negative collecting plate 150 against thenegative electrode foil lower end 117 a of the negative electrode plate116 can cause the convex ridges 155 to bend the negative electrode foillower end 117 a of the negative electrode plate 116 inward. Therefore, acontact area between the convex ridges 155 and the negative electrodeplate 116 becomes large to allow flow of a large amount of electriccurrent therethrough.

The positive collecting plate 120 is constructed such that a projection122 is formed centrally of a disk 121 and a plurality of convex ridges125 extend radially toward an outer periphery of the disk 121 from theprojection 122. Like the convex ridges 155 of the negative collectingplate 150, the respective convex ridges 125 are tapered to be increasedin height toward the outer periphery of the disk 121 from a centerthereof. Therefore, pressing the convex ridges 125 against the positiveelectrode foil upper end 114 a of the positive electrode plate 113 cancause the positive electrode foil upper end 114 a to be bent inward.Therefore, like the negative electrode plate 116, a contact area betweenthe convex ridges 125 and the positive electrode plate 113 becomes largeto allow flow of a large amount of electric current therethrough.

The projection 122 has an opening 122 a, and a safety valve 127 ismounted on the opening 122 a.

The outer packaging can 130 is a storage casing formed of anelectrically conductive material in the form of a bottomed cylinder. Theouter packaging can 130 is formed at a center of a bottom 131 thereofwith an opening 131 a. An opening 136 is formed on an upper portionopposite to the bottom 131. The small diameter portion 152 b of theprojection 152 on the negative collecting plate 150 is inserted into theopening 131 a whereby the step 153 of the projection 152 can be broughtinto contact with the bottom 131 of the outer packaging can 130. Thus acontact area between the bottom 131 and the negative collecting plate150 becomes large to allow flow of a large amount of electric current.

The cover 140 comprises an outer ring 141 and a central cylindricalportion 142, each of which is formed of an electrically conductivematerial and both of which are joined by an insulating ring 144. Thering 141 is welded to an opening 136 of the outer packaging can 130 toclose the outer packaging can 130. In this manner, the cover 140 can bemore rigidly mounted to the outer packaging can 130 by welding the ring141 to the outer packaging can 130 than by mounting with caulking.

The cylindrical portion 142 extends upward above a hole 145 formedcentrally of the cover 140. The projection 122 of the positivecollecting plate 120 is inserted into an insertion port 143 of thecylindrical portion 142 to be welded to an inner peripheral surface 146of the cylindrical portion 142 at a weld 147. At this time, theprojection 122 on the positive collecting plate 120 is inserted into theinsertion port 143 to such an extent that the projection 122 is notprojected above an upper end of the cylindrical portion 142, and weldingis carried out as described above to seal the electric double layercapacitor 100. The cylindrical portion 142 accommodates themanufacturing error of the electrode rolled body 112 and makes the sameadjustable by sliding the projection 122 in the insertion port 143 upand down. The relationship between the cylindrical portion 142 and theprojection 122 will be described in details with reference to FIGS. 12to 14.

In FIG. 4, the positive collecting plate 120 has the projection 122centrally of the disk 121. The positive collecting plate 120 has aplurality of the convex ridges 125 extending radially from theprojection 122. The convex ridges 125 extend downward to be directedtoward an upper end of the electrode rolled body 112. Openings 126 arerespectively formed between adjacent convex ridges 125.

The convex ridges 125 are pressed against the positive electrode foilupper end 114 a of the positive electrode plate 113 (see FIG. 3) wherebybent portions 114 b (see FIG. 3) are formed on the positive electrodefoil upper end 114 a of the positive electrode plate 113 only atlocations corresponding to the convex ridges 125. Therefore, theopenings 126 can be arranged in positions where the positive electrodefoil upper end 114 a of the positive electrode plate 113 is not bent.

FIG. 5 shows the electrode rolled body 112 in a state, in which the bentportions 114 b are formed on the positive electrode foil upper end 114 aof the positive electrode plate 113.

In this manner, since the bent portions 114 b are formed at locationscorresponding to the convex ridges 125 shown in FIG. 4, it is possibleto provide spaces between the positive electrode foil upper end 114 aand the positive electrode foil upper end 114 a in regions except thebent portions 114 b. Therefore, the openings 126 shown in FIG. 4 aredisposed above the spaces to permit the electrolyte to be easily pouredinto the electrode rolled body 112 through the spaces from the openings126.

FIG. 6 shows a state, in which the positive collecting plate 120 isplaced on the positive electrode foil upper end 114 a of the positiveelectrode plate 113.

A plurality of the openings 126 formed on the positive collecting plate120 are formed to be tapered such that their diameter on a front side ofthe disk 121 is larger than that on a rear side thereof. Therefore, pins162, 162 on a positioning jig 160 shown by two-dot chain line are easilyinserted into the respective openings 126 to position the positivecollecting plate 120 in a normal position.

How to mount the positive collecting plate on the electrode rolled bodywill be described below with reference to FIGS. 7A to 7F.

In FIG. 7A, the positive collecting plate 120 is placed on an upper endof the electrode rolled body 112, that is, the positive electrode foilupper end 114 a of the positive electrode plate 113, as shown by arrows{circle around (1)}.

In FIG. 7B, the pins 162, 162 of the positioning jig 160 are insertedinto the openings 126, 126, as shown by arrows {circle around (2)}.Since the openings 126, 126 are formed to be tapered as described above,the pins 162, 162 are smoothly inserted into the openings 126, 126.

In FIG. 7C, the pins 162, 162 of the positioning jig 160 shown in FIG.7B are fitted into the openings 126, 126 shown by hatch, among theopenings 126, 126 in the positive collecting plate 120, whereby thepositive collecting plate 120 can be positioned in a normal position,that is, in a position where the convex ridges 125 on the positivecollecting plate 120 are made to correctly register with X-axis andY-axis.

In FIG. 7D, the convex ridges 125 on the positive collecting plate 120are pressed against the positive electrode foil upper end 114 a of thepositive electrode plate 113 as shown by arrows {circle around (3)} tobend the positive electrode foil upper end 114 a inward to form the bentportions 114 b.

In FIG. 7E, for example, an electron beam welding apparatus 165 (seeFIG. 7F) is used to weld the convex ridges 125 to the bent portions 114b shown in FIG. 7D. Here, the convex ridges 125 on the positivecollecting plate 120 are positioned on X-axis and Y-axis as shown inFIG. 7C. Accordingly, the electron beam welding apparatus 165 is movedalong the X-axis and Y-axis, and hence the electron beam weldingapparatus 165 moves along the convex ridges 125 of the positivecollecting plate 120 as shown by an arrow {circle around (4)}.Therefore, it is possible to weld the convex ridges 125 to the bentportions 114 b as shown in FIG. 7F. Accordingly, a large contact areacan be ensured between the convex ridges 125 of the positive collectingplate 120 and the bent portions 114 b , so that the convex ridges 125and the bent portions 114 b are sufficiently adhered to each other.

In this manner, the electron beam welding apparatus 165 is set so as tomove in a direction shown by the arrow {circle around (4)} along theX-axis and Y-axis as shown in FIG. 7E. Therefore, when the convex ridges125 on the positive collecting plate 120 are offset from the X-axis andY-axis as shown in FIG. 8A, the electron beam welding apparatus 165 willmove in a position offset from the convex ridges 125.

Then, the electron beam welding apparatus 165 becomes offset from theconvex ridges 125 (see FIG. 8A) of the positive collecting plate 120 asshown in FIG. 8B, so that the electron beam welding apparatus 165 willperform welding on only a tip end of the positive electrode foil upperend 114 a of the positive electrode plate 113. Therefore, a contact areabetween the convex ridges 125 on the positive collecting plate 120 andthe positive electrode foil upper end 114 a of the positive electrodeplate 113 becomes small not to enable adequately ensuring closeadherence between the convex ridges 125 and the positive electrode foilupper end 114 a.

FIG. 9A schematically shows another embodiment of the invention, andFIG. 9B shows a comparative example.

In FIG. 9A, openings 126 in the positive collecting plate 120 arepositioned distant from bent portions 114 b (see FIG. 5) on positiveelectrode foil upper ends 114 a. Therefore, the openings 126 arepositioned in spaces between the positive electrode foil upper ends 114a. Accordingly, when the electrolyte 137 is filled in, it rapidly entersand fills into the electrode rolled body 112 through the spaces betweenthe positive electrode foil upper ends 114 a from the openings 126 asshown by arrows {circle around (5)}.

As shown in FIG. 9B, however, if the openings 126 of the embodiment werenot formed in the positive collecting plate 120, the electrolyte 137would flow to an outer peripheral portion of the electrode rolled body112 from an outer peripheral portion of the positive collecting plate120, as shown by arrows {circle around (6)}. Therefore, it would bedifficult to rapidly fill the electrolyte into the electrode rolled body112 from a side of an upper end of the electrode rolled body 112, and itwould take time in fully filling the electrolyte.

First and second modifications of his embodiment will be describedbelow. invention and a divisional application may be filed.

FIG. 10 is a plan view showing a positive collecting plate in anelectric double layer capacitor according to the first modification.

In FIG. 10, a positive collecting plate 220 in an electric double layercapacitor 200 is constructed to comprise eight radial, convex ridges 225formed equidistantly, and eight openings 226 formed between adjacentconvex ridges 225.

In this manner, with the first modification. the openings 226 areincreased in number, and so are formed over the entire positivecollecting plate 220 to permit an electrolyte to be efficiently filledinto the electrode rolled body 112 (see FIG. 3). Further, an increase innumber of the convex ridges 225 makes rigid mounting of the positivecollecting plate 220 to the electrode rolled body 112.

FIG. 11 is a plan view showing a positive collecting plate in anelectric double layer capacitor according to the second modification.

A positive collecting plate 320 in an electric double layer capacitor300 according to the second modification is cross-shaped by formingcurved notches 326 from a disk. The cross-shaped, positive collectingplate 320 is formed with cross-shaped, convex ridges 325 so as toconform to its configuration. The notches 326 correspond to the openings126 of the second embodiment and to the openings 226 of the firstmodification.

Thus notches 326 are formed to be curved to thereby provide largeopenings between adjacent convex ridges 325, so that an electrolyte canbe efficiently filled into the electrode rolled body 112.

While the openings 126 or 226 shown in the second embodiment or in thefirst modification are examples in the form of a circle, the inventionIs not limited to the embodiment and the modification but aconfiguration of the openings may be, for example, rectangular ortriangular.

The relationship between the cover 140 and the positive collecting plate120 shown in FIG. 3 will be described hereinbelow with reference toFIGS. 12A to 14.

In FIG. 12A, after the electrode rolled body 112 is wound in a rolledmanner, the negative collecting plate 150 is mounted to the negativeelectrode foil lower end 117 a of the negative electrode plate 116, andthe positive collecting plate 120 is mounted to the positive electrodefoil upper end 114 a of the positive electrode plate 113. Then, theelectrode rolled body 112 in this state is received in the outerpackaging can 130 through the opening 136, and the small diameterportion 152 b of the projection 152 formed on the negative collectingplate 150 is inserted into the opening 131 a formed in the bottom 131 ofthe outer packaging can 130 as shown by an arrow {circle around (1)}.

In FIG. 12B, the cover 140 is covered from above the outer packaging can130 as shown by arrows {circle around (2)} to close the opening 136 ofthe outer packaging can 130. At the same time, the projection 122 on thepositive collecting plate 120 is fitted into the insertion port 143 ofthe cylindrical portion 142 on the cover 140.

In FIG. 13, (a) shows the relationship between the cylindrical portion142 and the projection 122 when the electrode rolled body is minimum inmanufacturing error, and (b) shows the same relationship when theelectrode rolled body is maximum in manufacturing error.

In FIG. 13(a), when the electrode rolled body is minimum inmanufacturing error, a dimension h of the electrode rolled body 112shown in FIG. 12B becomes minimum. Accordingly, when the projection 122on the positive collecting plate 120 is fitted into the insertion port143 of the cylindrical portion 142, an upper end 122 b of the projection122 projects slightly above the insertion port 143 of the cylindricalportion 142. That is, the upper end 122 b of the projection 122 enterssufficiently below an upper end 142 a of the cylindrical portion 142.

In FIG. 13(b), when the electrode rolled body is maximum inmanufacturing error, the dimension h of the electrode rolled body 112shown in FIG. 12B becomes maximum. Accordingly, when the insertion port143 of the cylindrical portion 142 is fitted onto the projection 122 onthe positive collecting plate 120, the upper end 122 b of the projection122 enters near an upper end 142 a of the cylindrical portion 142. Thatis, the upper end 122 b of the projection 122 shown in (b) is positionedat a level higher than the upper end 122 b of the projection 122 shownin (a) by Δh.

That is, when the manufacturing error of the electrode rolled body is inthe range of Δh. the projection 122 does not project above thecylindrical portion 142. so that it is possible to accommodate themanufacturing error of the electrode rolled body. In other words, Δh ofthe manufacturing error of the electrode rolled body 112 (see FIG. 12B)is allowable.

When the position of the electrode rolled body within the outerpackaging can is determined, welding is performed on various locationsas shown in FIG. 14,

In FIG., 14, welding is first applied between the opening 136 of theouter packaging can 130 and the ring 141 of the cover 140 to seal theopening 136. Then, welding is applied between the bottom 131 of theouter packaging can 130 and the small diameter portion 152 b of theprojection 152 to close the opening 131 a . Further, the cylindricalportion 142 and the projection 122 are welded to each other at the innerperipheral surface 146 of the cylindrical portion 142 to seal a gaptherebetween with the weld 147.

As a reference dimension H of the electric double layer capacitor 100 isset to a dimension between the bottom 131 of the outer packaging can 130and the upper end 142 a of the cylindrical portion 142, it is keptuniform unless the projection 122 projects above the upper end 142 a ofthe cylindrical portion 142.

In this manner, even when the electrode rolled body 112 experiencesmanufacturing error, the manufacturing error of the electrode rolledbody 112 can be accommodated by moving the projection 122 verticallywithin the cylindrical portion 142. Therefore, a relatively largemanufacturing error Δh (see FIG. 13) is made allowable in manufacture ofthe electrode rolled body 112, and so the manufacture becomes easy.

As described above, the small diameter portion 152 b of the negativecollecting plate 150 is inserted into the opening 131 a of the outerpackaging can 130, and the outer packaging can 130 and the smalldiameter portion 152 b are welded to each other. In addition, theprojection 122 on the positive collecting plate 120 is inserted into thecylindrical portion 142 of the cover 140, and the projection 122 iswelded to the cylindrical portion 142. Therefore, the lower end of theelectrode rolled body 112 is rigidly mounted to the outer packaging can130, and the upper end of the electrode rolled body 112 Is rigidlymounted to the cover 140, whereby the vibration-proof quality of theelectric double layer capacitor 100 is improved.

Further, because the projection 152 is formed on the negative collectingplate 150 and the small diameter portion 152 b of the projection 152 isinserted into the opening 131 a of the outer packaging can 130 to applywelding between the outer packaging can 130 and the small diameterportion 152 b, a contact area between the outer packaging can 130 andthe small diameter portion 152 b becomes large. Therefore, contactportions between the respective parts allow flow of a relatively greatelectric current.

In the embodiment, while the opening 131 a is formed in the bottom 131of the outer packaging can 130 and the projection 152 (the smalldiameter portion 152 b) of the negative collecting plate 150 is insertedinto the opening 131 a, the invention is not limited to such anarrangement and the projection 152 of the negative collecting plate 150may not be inserted into the bottom 131 of the outer packaging can 130.

Obviously various minor changes and modifications of the presentInvention are possible in the light of the above teaching. It istherefore to be understood that within the scope of the appended claims,the invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. An electric double-layer capacitor having anelectrode rolled body obtained by overlapping and winding a pair ofelectrode plates, which serve as positive and negative electrodes, andpositive and negative collecting plates, which are mounted to upper andlower ends of the electrode rolled body through which charging iseffected on the electrode plates and discharging is effected from theelectrode plates, characterized in that at least the positive collectingplate of the collecting plates includes a plurality of convex ridgesextending radially from central portions thereof and projecting towardthe electrode rolled body, the plurality of convex ridges are pressedagainst the electrode rolled body to form bent portions on upper andlower ends of the electrode plates, the convex ridges are joined to thebent portions by welding, and openings or notches are each positionedbetween adjacent two of the bent portions formed by adjacent two of theconvex ridges, respectively, to permit an electrolyte to be filled intothe electrode rolled body through the openings or notches.
 2. Anelectric double layer capacitor according to claim 1, wherein each ofthe plurality of convex ridges is tapered to be increased in heighttoward an outer periphery thereof from a central portion thereof.